The present invention relates to a new and improved construction of connection coupling which can be coupled or connected under pressure and serving for use with hydraulic lines or conduits.
Generally speaking, the connection coupling of the present invention is of the type having a non-pressure loaded coupling half and a coupling half which is under pressure load. A valve guide is centrally arranged in each coupling half. In each valve guide there is axially displaceably arranged a respective spring-loaded, hydraulically impingeable valve in a manner such that the valve heads of such valve, during the coupling operation, are pressed against one another. The non-pressure loaded valve is shifted through twice the possible valve stroke or displacement path of the pressure loaded valve, and the non-pressure loaded valve is loaded with a spring which is stronger than the spring loading the pressure loaded or pressure impinged valve, so that with pressure equalization the previously pressure loaded valve is pressed, in the open position, against a stop provided at the previously pressure loaded coupling half and there results a maximum valve-passage cross-section at both valves.
Connection couplings of this type work completely satisfactorily during normal operation, in other words when the hydraulic fluid always flows in the same direction from the non-pressure loaded coupling half to the pressure loaded coupling half. But already, however, upon occurrence of pronounced pressure fluctuations and pressure surges, causing a reversal of the flow direction, the valve which previously was under pressure can slam shut since the oppositely situated valve is not fixed in its position. Without exception such type connection couplings can not be employed when the direction of flow of the hydraulic fluid or liquid medium, during operation, reverses, under circumstances even in a sudden-like manner, and thus, also the valve is slammed shut. This occurs, for instance, if there are provided double-acting cylinders in hydraulic installations wherein the pressure line and return flow line are identical. An increase of the pressure normally prevailing in such type hydraulic installations additionally can be brought about when the weight at the load-side of the device loads the corresponding piston, such as for instance is the case during lowering of a fully loaded front loader.
Also as part of the state-of-the-art is a connection coupling wherein the free path of the previously non-pressure loaded valve can be limited following the coupling operation, to thereby preclude any return movement or retraction of the valve. Such adjustment of the coupling has, however, been found to be really disadvantageous, firstly because to do so there is required an appropriate tool, and thus, frequently cannot be carried out, or because the adjustment is totally forgotten since the described drawback first is noticeable during operation.